1. Field of the Invention
The present invention relates to a deterioration degree calculating method, a control method, and a control device for a lithium ion secondary battery.
2. Description of Related Art
In this specification, “lithium ion secondary battery” refers to a secondary battery in which lithium ions are used as electrolyte ions, and charge and discharge are realized by electrons moving between positive and negative electrodes along with the lithium ions. Here, the form of “lithium ion secondary battery” which is a control target of the control device includes “battery pack” in which plural battery elements are connected to each other. Further, the form of “lithium ion secondary battery” which is a control target of the control device includes a secondary battery which is incorporated into “the battery pack” as a battery element.
As a control method for a lithium ion secondary battery, Japanese Patent Application Publication No. 2013-89424 (JP 2013-89424 A) discloses a method for estimating deterioration of a battery. In the estimation method disclosed in JP 2013-89424 A, a data table for estimating to what degree a battery deteriorates when being left to stand at a temperature in a SOC for a predetermined amount of time, is prepared. In practice, a deterioration degree of the battery is estimated based on a temperature history and a SOC history.
Regarding the method for estimating a deterioration degree of a lithium ion secondary battery, the method disclosed in JP 2013-89424 A can estimate a deterioration degree of a lithium ion secondary battery. However, it is preferable that a difference between a deterioration degree, which is calculated as an estimated value, and an actual deterioration degree of the lithium ion secondary battery is small. Here, a new method capable of accurately estimating a deterioration degree of a lithium ion secondary battery is disclosed.